The present invention relates, in general, to electronic engineering and, more specifically, concerns the method of manufacturing the magnetic medium for data storage.
Known in the present state of art is the method of magnetic medium for data storage, said medium appearing as a nonmagnetic matrix incorporating particles of a magnetic material distributed thereover and kept out of contact with each other (cf. U.S. Pat. No. 5,652,054, NPC 428-328, 1997). According to said patent, a desired magnetic medium for data storage is prepared by simultaneous magnetron sputtering of the material of said nonmagnetic matrix and said magnetic material and their vacuum co-deposition on a substrate made of glass, ceramics or metal. Sputtering the material of the nonmagnetic matrix and of the magnetic material in an inert gas, or their chemical deposition from gaseous phase can be used as well. However, the method in question fails to provide a clear-cut regular distribution of magnetic particles in the matrix and prevents attaining identical geometric dimensions and shapes of the magnetic particles and their equal spacing from one another.
Known in the present state of the art is a method of manufacturing magnetic medium for data storage which appears as a matrix made from a nonmagnetic material and having equally sized and shaped magnetic segments spaced equally apart from one another on said matrix and featuring shape anisotropy ensuring two stable magnetized states (cf. U.S. Pat. No. 5,820,769, NPC 216-22, 1998). The production process techniques protected by said patent makes use of an electron-beam lithography procedure comprising the steps of: establishing, on a nonmagnetic substrate, a protective mask made of a resist, i.e., polymethylmethacrylate (PMMA); focusing an electron beam on said resist until a dia. 4 nm spot is obtained; etching said nonmagnetic substrate to form holes therein unprotected by said resist; applying, either by spray-deposition or photo-deposition, a magnetic material to said nonmagnetic substrate; removing said resist from said nonmagnetic substrate; and filling the space confined between the thus-formed segments of the magnetic material, with a nonmagnetic material, e.g., an insulator.
The aforementioned method allows of obtaining relatively large-sized magnetic segments being 120 nm long and 35-40 nm in diameter, that is, shape anisotropy is characterized by a length-to-diameter ratio ranging between 3-3.4 with the spacing between the magnetic segments being from 50 to 1000 nm. However, the density of data recorded on such a medium is rather low, while a relatively weak shape anisotropy affects adversely reliability of storage of recorded data due to spontaneous reversal of magnetization of the magnetic segments caused by nonobservance of some conditions for the magnetic medium exploitation (e.g., absence of magnetic and electromagnetic fields, effect of heat, etc.).
Selected as the prototype of the present invention is a method of manufacturing the magnetic medium for data storage known from the specification of Japanese Application #3-254,421, IPC G 11 B 5/84, 1991. According to said method, a 1 xcexcm thick layer of a soft magnetic material having high magnetic permeability is either electroplated or spray-deposited on a nonmagnetic substrate. Then a mask is formed on the thus-prepared layer using photolithography technique, whereupon said layer of soft magnetic material is exposed to the effect of a flux of hydrogen or helium ions. Thus, hydrogen or helium ions are free to implant into those portions of said layer which are not protected by the mask during the exposing process so as to transform magnetic properties of said layer at the place of their implantation, i.e., nonmagnetic segments in the layer are generated as a result.
Once the photolithographic mask has been removed, the layer deposited on the substrate comprises both magnetic segments adapted for data storage, and nonmagnetic segments resulting from carrying out the present method and alternating with said magnetic segments in accordance with the pattern of the photolithographic mask.
However, the method under discussion fails to be capable of manufacturing the magnetic medium for data storage that ensures high-density data recording nor does it provide for a very pronounced shape anisotropy of the magnetic segments of the data carrier which may lead to a spontaneous externally induced change in the magnetization vector and, hence, to loss of recorded data.
The present invention has for its primary and essential object to provide a method of manufacturing the magnetic medium for data storage that makes it possible to attain higher density of recorded data and add to reliability of its storage due to a change in the composition and structure of a material capable of varying its magnetic characteristics under the effect of irradiation. Said object is accomplished due to the provision of a method of manufacturing the magnetic medium for data storage, said method comprising the following steps: laying on a nonmagnetic substrate a layer of a material capable of varying its magnetic characteristics under the effect of irradiation; selectively irradiating said layer with a flux of charged particles so as to vary magnetic characteristics of the material of said layer on the irradiated segments thereof; forming in said layer regularly alternating nonmagnetic and magnetic segments, wherein, according to the present invention, used as the material capable of varying its magnetic characteristics, is a material having a low or zero initial magnetization; irradiating said layer until magnetic segments are formed therein, each of the thus-formed magnetic segments having a maximum overall size the ratio between which and any other overall size of said magnetic segment being from 3.5:1 to 15.0:1, the thickness of said layer being equal to one of the overall size values of any one of the magnetic segments being formed.
It is due to the present invention that it becomes possible to make the magnetic medium for data storage capable of high density and reliable storage of recorded data.
In accordance with the present invention, it is expedient that said selective irradiation of said layer be effected using a mask applied to the layer of the material capable of varying its magnetic characteristics under the effect of irradiation.
According to the invention, it is expedient that said selective irradiation of said layer be effected using a stencil placed in front of the layer being irradiated.
According to the invention, it is expedient that used as the material capable of varying its magnetic characteristics are nonmagnetic compounds of ferromagnetics.
According to the invention, it is expedient that when manufacturing the magnetic medium for data storage adapted for perpendicular data recording, a layer of the material capable of varying its magnetic characteristics has a thickness selected to be from about 10 nm to about 500 nm.
According to the invention, it is expedient that when manufacturing the magnetic medium for data storage adapted for longitudinal data recording, a layer of the material capable of varying its magnetic characteristics has a thickness selected to be from about 2 nm to about 50 nm.
According to the invention, it is expedient that a protective layer be applied to the layer having regularly alternating magnetic and nonmagnetic segments.